“Among other things, it appears that your clients may have reviewed, shaped and edited the false statement that Cohen submitted to the Committee, including causing the omission of material facts,” Schiff wrote in a May 3 letter to attorneys for the lawyers, which was obtained from a committee source. “In addition, certain of your clients may have engaged in discussions about potential pardons in an effort to deter one or more witnesses from cooperating with authorized investigations.”

Cohen testified publicly before the House Oversight and Reform Committee in February that changes were made to his statement after Trump’s lawyers reviewed it. He also provided closed-door testimony to the House Intelligence Committee as part of its revived and expanded investigation into foreign interference and Trump’s dealings with Russia.

Sekulow vehemently denied that attorneys for the president edited or changed Cohen’s statement to Congress to alter the duration of the Trump Tower discussions.

Patrick Strawbridge, a lawyer for Sekulow, accused Schiff of pursuing a "needless dispute" in a statement on behalf of the group of attorneys.

"Instead of addressing important intelligence needs, the House Intelligence Committee appears to seek a truly needless dispute — this one with private attorneys — that would force them to violate privileges and ethical rules," Strawbridge said. "As committed defense lawyers, we will respect the constitution and defend the attorney-client privilege — one of the oldest and most sacred privileges in the law."

The committee first sent a document request to Sekulow and other lawyers on March 14, asking for a slew of documents, including those related to the drafting of Cohen’s statement on the Trump Tower Moscow project, false statements he made to Congress in relation to that statement, discussions for a possible pardon of Cohen and other matters.

Schiff also asked the lawyers to submit to voluntarily transcribed interviews with the committee. He set a March 22 deadline for them to comply with the requests.

The lawyers through their own counsels declined to comply with the document request or submit to interviews on April 5, describing the requests as “unprecedented” and outside the scope of the panel’s oversight authorities in a letter to the committee. They also claimed the information requested would fall under attorney-client privilege.

“Although the Committee has important responsibilities over this country’s intelligence agencies, we are at a loss to see how that charge justifies your sweeping and unprecedented requests to our clients,” the letter states.

“Absent a sufficient justification for these requests, our clients cannot agree to provide the requested documents or submit to an interview,” it adds. “That is particularly true since your requests plainly target information that would fall within the attorney-client privilege and work-product privileges.”

Schiff pushed back on their arguments in the latest letter, arguing that the objections to the request “lack merit and establish no valid basis to withhold the requested documents and testimony from the committee.”

The chairman also set a new deadline of May 10 for the lawyers to comply with the requests.

A senior committee official told The Hill on Tuesday that the lawyers had not yet responded to the second letter but that Schiff was prepared to issue a subpoena to compel their cooperation if needed.

“Material in the Committee's possession, as well as Michael Cohen's Committee testimony and admissions to the Special Counsel's Office, raise serious, unresolved concerns about the obstruction of our Committee's investigation that we would be negligent not to pursue,” Schiff said in a statement Tuesday.

“If any individual is allowed to lie to our committee or encourage others to do so, hide behind inapplicable privileges, or otherwise fail to provide anything less than full cooperation, other witnesses will be emboldened to similarly obstruct, both now and in the future. We must not allow that to happen,” Schiff continued.

Updated at 6:11 p.m.

CORRECTION: The House Intelligence Committee is investigating whether lawyers working for both Trump and members of his family interfered in panel's Russia investigation. An earlier headline included incorrect information.